Most men when they hit their 30s really don't feel like doing the things they thought was fun in your 20s. For me, when I hit my mid 30s I lost all interest in going 'clubbing'. I would have stopped sooner, but in my 30s I was living in Europe, so it was all sort of new and interesting, but after a couple of years doing that... I was partied out.
After my divorce in my mid-40s, I got back on the wagon again, but quickly figured out I just couldn't do it anymore without screwing up my health and purpose.
I definitely had the energy to do it in my 30s, I just really didn't want to any more.